To adjust effective diameter of pulleys in hydraulically and/or pneumatically controlled V-belt drives in continuously variable transmissions, known control devices rely on mechanical linkage to transmit a change in the position of the accelerator pedal so as to turn a cam plate which acts on a control element. Such continuously variable transmissions are used, e.g., in the interest of fuel efficient operation of a combustion engine. To this effect, control of the transmission aims at adjustment of transmission ratio so as to allow the engine of a vehicle to operate at optimal rotational rate and to produce optimal torque (optimal with respect to fuel efficiency) under all load conditions. Known control devices tend to be difficult to adjust to different types of combustion engines having different characteristics of optimal torque; moreover, mechanical transmission of the position of the accelerator pedal may be subject to linkage errors.